1. Technical Field
The present invention relates to mechanisms for converting linear reciprocating motion to rotary motion and, more particularly, to such mechanisms wherein the resulting rotary motion is unidirectional. The invention has particular utility in applications where combined linear reciprocation and unidirectional rotation are required.
2. Discussion of the Prior Art
There is known in the prior art a certain type of mechanism for converting linear reciprocation to rotational oscillation. Such mechanisms are exemplified by the apparatus disclosed in the following documents: U.S. Pat. No. 1,173,326 (Taylor); U.S. Pat. No. 308,523 (Sergeant); U.S. Pat. No. 4,265,434 (Hamilton et al); U.S. Pat. No. 4,484,510 (Hirzel); International Publication No. WO82/04293 (Archer et al); and USSR Patent No. 222,095 (Kheyfets). Apparatus of this type includes a reciprocated piston, typically driven pneumatically or hydraulically, having a helical groove of defined length in its periphery. A guide member, such as a pin, ball or other projection, extends from the piston housing into the groove, forcing the piston to rotate about its axis in response to linear piston displacement. As the piston is linearly reciprocated, the guide member and groove arrangement causes the piston to rotate in a oscillatory manner; that is, the piston rotates in one direction in response to distal piston displacement, and in a second direction in response to proximal piston displacement.
For certain applications it is desirable to have continuous linearly reciprocating motion combined with unidirectional rotation, e.g., impact drills. The prior art mechanisms described above are incapable of rotating the piston in only one direction. On the other hand there are other prior art drive mechanisms that combine rotary movement and linearly reciprocating movement, but those mechanisms use continuous rotation movement as the primary movement to produce superimposed linear reciprocation.